Let's start with colon cancer and rectal cancer. There are many therapy options available today for colorectal cancer. How to choose the right treatment? What are the goals of preoperative staging in colon cancer and rectal cancer? Preoperative staging is very very important in colorectal cancer. It is true with any kind of cancer. It helps you to determine the better treatment for the patient. you start with ruling out metastatic disease. It means that you want to ensure that colon cancer or rectal cancer did not spread to the liver or to the lungs or to other organs. You have to exclude metastatic cancer in colon cancer. Then you can perform surgery. Situation is different in rectal cancer. There is more tumor staging that we can do in the rectal cancer. Diagnostic imaging available now allows us to determine the local stage of rectal cancer. We are able to see preoperatively the lymph nodes. They could be enlarged. It means that they could be positive for cancer. We can see the extent of the invasion into the rectal wall. Invasion happens in T3 or T4 stage tumor. Rectal cancer can be “locally advanced”. Then you see positive lymph nodes for tumor. Patients with a T3 or T4 tumor will benefit from neoadjuvant therapy. It could be a standard neoadjuvant chemotherapy and radiation therapy. But there are protocols of the investigative clinical trials. These are testing experimental preoperative chemotherapy for patients with rectal cancer. Clinical trials are done more often for patients with rectal cancer and colon cancer. Patients with colorectal cancer often require both MRI and CT imaging. That's correct. For rectal cancer, rectal MRI is very important. Transrectal ultrasound is also required. In colon cancer MRI plays an important role. You may see suspicious lesions on a CT scan in colon cancer. Then you want to make sure that those lesions are not metastatic tumors. Then you would do a liver MRI in colon cancer. You have to rule out metastatic disease. Of course, when the patient is newly diagnosed with cancer, you also do a “metastatic survey” in patients. “Metastatic survey” includes the CT scan of the chest, abdomen, and pelvis. That's the best method to stage colorectal cancer before treatment. Staging of cancer means determining the extent of cancer. You may be dealing with recurrent colorectal cancer. Then PET CT imaging is useful. But initial evaluation of colorectal cancer involves a CT scan of the chest, abdomen, and pelvis. CT and MRI scans help to determine the stage of colon cancer. Diagnostic imaging also helps to determine the correct treatment. It might not necessarily be surgical operation first. You mentioned the neoadjuvant chemotherapy treatment. This is a cancer treatment before actual surgery happens. Exactly. In rectal cancer a patient undergoes preoperative chemotherapy and radiation therapy. Or just chemotherapy. In colon cancer usually patients proceed straight for surgical operation. Sometimes you do have metastatic disease though. A lot of times these patients benefit from systemic chemotherapy. Then the decision is made if they are good candidates for the surgical treatment. Surgery can involve metastases removal. Surgeons could also remove a primary colon cancer or rectal cancer tumor.